1. Field of the Invention
This disclosure generally relates to load stabilization for machines powered by fuel cells.
2. Description of the Related Art
The “fuel” powering an alternating current (“AC”) machine, such as a field-oriented induction motor, is current. This current may be divided into two components, torque current and flux current. Torque current may be viewed as that component of the current which generates motive force, or torque. Flux current may be viewed as that component of the current which generates magnetic flux in the rotor of the machine. Torque and flux currents in induction motors are discussed in more detail in co-pending U.S. patent application Ser. No. 10/345,872 filed Jan. 15, 2003, which is entitled Overmodulation Systems and Methods For Induction Motor Control and which published on Sep. 4, 2003 under Publication No. 20030164028, and in a February 1998 publication by Texas Instruments Europe bearing Literature No. BPRA073 and entitled Field Oriented Control of 3-Phase AC-Motors, which are incorporated herein by reference in their entirety.
AC machines, such as induction motors and/or generators, are often employed in electric and hybrid vehicles, which typically employ fuel cells, batteries and/or super- or ultra-capacitors as a power source. Current is supplied to windings through a power subsystem, typically comprising an inverter. Power subsystems typically employ power semiconductor devices, such as insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), and/or semiconductor diodes.
Fuel cells, batteries and/or super- or ultra-capacitors can be sensitive to sudden changes in load, which can result in a reduction in the performance and/or long-term life of a fuel cell stack, battery array and/or super- or ultra-capacitor arrays. Accordingly, it can be appreciated that there is a need for a system and method for stabilizing a load presented to a fuel cell stack, a battery array, and/or a super- or ultra-capacitor array.